The present invention relates to sheet-feed tractors of the type used, for instance, in automated printers for computers and word processors.
The broad claims of the copending application of Alan F. Seitz, Ser. No. 305,492 filed Sept. 25, 1981, for a Manually Assemblable Sheet-Feed Tractor are directed to a concept, disclosed in that application, that includes the use of the clamp parts of the tractor to hold together the frame members. In the initial version of that concept, a tab on the outer surface of one clamp part was engaged by an engagement surface on the other clamp part throughout a range of rotational orientations of the second clamp part so that the second clamp part would be held in place throughout that range and would in turn hold the frame parts together. In a position outside of that range of rotational orientations, a slot would register with the tab, and the second clamp part would be permitted to be removed axially.
As those skilled in the art will recognize, this concept is quite advantageous, permitting assembly and disassembly to be carried out on a repetitive, assembly-line basis without the necessity for tools or special fixtures.
It is the object of the present invention to improve the basic concept by enhancing the stability of the frame members toward their ends and thereby add to the reliabiiity with which the frame members hold the sprocket and belt in place at the ends of the frame members.